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Mk2 Vitesse still not running right


Paul H
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Plus Hi my Vitesse mk2 is still not not running right . She goes through the gears fine and at 30 to 40 mph cruising fine. Then at close to 50mph and 3,000 revs she becomes hesitant as if there is a fuel issue . I remember quite well what Pete told me “ the solution to the problem is not the answer “ so here is my analysis 

  1. The carbs are cdse with the emission controls blocked off and B5CF needles . I have balanced the carbs with an ear tube and the mixture seems ok , lifting the needle holder a nidge with a flat head screwdriver there is no discernible change in engine revs . The carbs are on max rich  now and the pic might suggest I might be able to back off half a turn . The plugs are all roughly the same colour though need a longer run to confirm this before I change the mixture . The pic was taken after just 10 min run so imo not a true picture , but to show there doesn’t seem to be a duff plug 
  2. My thoughts in line with a previous post suggested the problem was fuel related / lean mixture so the only other thing to try was to revert to the original engine mounted fuel pump as I had converted to a Huco pull pump in the engine bay . The change back made no difference other than the engine needs an additional tug to get started due to the Huco electric pump . With the Huco she will start on second tug and then first time when she is warm. 
  3. So if it’s not fuel it must be electrics 
  4. The Distributor is a new Delco with Accuspark ignition . I can change back to Lucas with traditional points 
  5. Try another coil
  6. Replace the spark plugs
  7. Change the HT leads 
  8. As to timing the PO added white marks on the pully and I’m running at 2 to 3 degrees more advanced than the white line
  9. The petrol is Tesco premium , recent purchase 

What should I try first and will make one change at a time so I can isolate the problem 

I would add that the engine was faultless to a T last year with 3k miles including 1600 miles round Ireland . The setup for last year was as current except for Lucas plus points for part of the time and Accuspark for the remaining . Plus the plugs are gapped at 30 tho now due to electronic ignition 

Any thoughts and input welcomed 

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My own experience of using 150CDSE carbs on the Mk2 was over a lack of bit in the throttle. Not a flat spot  more like a flat performance. I put the standard 150CDS carbs on and it woke the engine up. The only thing I can put it down to was the needle profile gave a weak mixture, but the plugs looked OK. That aside maybe check the emission valve, oil in the dashpots and try a different brand of fuel.

It difficult to come up with anything you haven't already covered.

Dave   

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I had a "soft" misfire on my GT6 which I traced to the incorrect setting of the spring "blade" on top of the Delco rotor arm. If it isn't set high enough it doesn't make proper contact with the dizzy cap centre electrode. This may not be your problem, but it is a simple enough check. I've attached a picture showing the dimension you're looking for

Wayne

IMG_0375.JPG

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If it were me, I'd put it back to standard points and re-gap the plugs to 25thou (Or standard if not 25!)

Are the leads holding onto the end of the spark plugs ok? I ask because I think that was one of my issues in that the rubber boot over the plug was tending to spring back and hence the spark had to jump twice!

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Now theirs a memory jogger from Wayne. Thanks.

The float chamber valves can stick, not fully closed, causing flooding if the car hasn't been unused for a while. If there is a strong smell of petrol around the carbs and or fuel is found in the air cleaners then it's flooding. Not an uncommon problem on carbs that have been standing. You can try before stripping down the carbs removing the fuel pipe and blasting out the valve with WD40.

Dave

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7 minutes ago, poppyman said:

Hi Paul, i see you are using NGK plugs. There has been discussion on here as to how good they are??  I have them in one of my car's without problem, but they are nos not recent purchase. Might be worth a try?

Tony. 

Hi Tony would a duff plug cause the problem ? 

Paul 

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Plugs...life and soul of  the engines performance

Those plugs look somewhat sooty

And it seems any plugs looking a bit off just dont work well , these days 

If you read the spark plug  post its beginning  to add up to ro what a number of us are finding

And  add when theres a problem under combustion pressures all hell breaks loose 

Pete

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1 minute ago, Pete Lewis said:

And  add when theres a problem under combustion pressures all hell breaks loose

Absolutely!

Around the turn of the millennium, I had a VW Passat (5-cyl 2L injection - a nice motor). It ran superbly until my local garage, being very helpful, "re-tuned it" (i.e. retarded the ignition) for unleaded, since 4* was about to disappear. After that it suffered a truly horrid misfire if I tried to accelerate from 30 in 4th. I put the ignition back to the 4* setting and it ran beautifully again.

The reason was that the whole ignition system was a little past its best, so the spark was a tiny bit weak. In 4* tune that wasn't a problem but 3deg extra retard meant, under those high load/low speed conditions, the in-cylinder pressure at the point of ignition was just a bit too high for a reliable spark.

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Could you run it for a while at the hesitant stage, then do a plug chop. It might show wetter/different colour, plug ( if ignition related from the segments of the dizzy cap to the plugs)/or 3 plugs, if one carb related).

could be way off with this, just an idea.

Dave  

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Thanks for all your replies. I will try a new set of plugs to see if that sorts the issue . If it doesn’t run the vitesse at 40 mph for 20 mins and check the plugs . Then run the vitesse at 50 mph for a short period and see if the plug colour changes . I will also accelerate through the 50 mph to see if it is a flat spot . 

If this achieves nothing change the distributor to Lucas with points 

Thanks again for your input 

Paul 

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3 hours ago, Paul H said:

Hi Tony would a duff plug cause the problem ? 

Paul 

Hi Paul, yes duff plug would cause the problem.... I would try a different make of plug first and see if the problem goes? If it does you know for sure what the problem was..... Try loads of things at once and you wont know what the main cause was, so dont worry to much on the plug colour at this stage. :) 

Tony.

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  • 2 weeks later...

UPDATE , changed the plugs , ht leads and the problem is still there though better defined as follows

She starts fine drives well on the flat at 40 mph ish then on my test route of 4 miles there is a long drag of a hill about 0.5 mile long . In the past I’ve been able to cruise up the hill with no issues at 60mph with or without overdrive now as soon as I hit the hill at 3k in 4th I get the start of the engine being “not happy “ and the engine faltering begins and clear signs something is wrong . After the hill it’s back to normal but keeping speeds to about 45 mph as the test run is on local roads . So where can I look to find the issue 

Paul 

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13 minutes ago, Paul H said:

UPDATE , changed the plugs , ht leads and the problem is still there though better defined as follows

She starts fine drives well on the flat at 40 mph ish then on my test route of 4 miles there is a long drag of a hill about 0.5 mile long . In the past I’ve been able to cruise up the hill with no issues at 60mph with or without overdrive now as soon as I hit the hill at 3k in 4th I get the start of the engine being “not happy “ and the engine faltering begins and clear signs something is wrong . After the hill it’s back to normal but keeping speeds to about 45 mph as the test run is on local roads . So where can I look to find the issue 

We had something similar, but a bit more intermittent, seemingly hot weather exacerbated the problem (we were in Iran and it was 40-45c!). Although it'd also start backfiring out the carb.Of course after fiddling around with things the problem would go away for an hour or so. I was convinced it was fuel vaporisation at the time.

It turned out to be a dodgy low tension lead (bad crimp) from the dizzy to the coil. I'd be tempted to change it as a matter of elimination. Although maybe this problem is perhaps more likely on a 4-cylinder with the coil on the bulkhead.

David

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2 minutes ago, JumpingFrog said:

We had something similar, but a bit more intermittent, seemingly hot weather exacerbated the problem (we were in Iran and it was 40-45c!). Although it'd also start backfiring out the carb.Of course after fiddling around with things the problem would go away for an hour or so. I was convinced it was fuel vaporisation at the time.

It turned out to be a dodgy low tension lead (bad crimp) from the dizzy to the coil. I'd be tempted to change it as a matter of elimination. Although maybe this problem is perhaps more likely on a 4-cylinder with the coil on the bulkhead.

David

Im running a Delco with Accuspark ignition - I will swop over to the Lucas 22d? with points to see if that makes a difference 

Paul 

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3 minutes ago, dave.vitesse said:

Could be lack of fuel. One of the locals had a similar problem and it came down to the needle float chamber valves in the carbs sticking. We cleaned the valves and opened up the float gap by a small about. It got rid of the problem. Maybe ?

Dave

Thanks Dave I’ve had issues before with float valves so will check again and check float valve clearance which should be 18mm . If this is the cause will the spark plug colour give a clue as to which carb . I will check both though 

Thanks

Paul 

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I see in the original post the timing is 'set 2 - 3 degrees more advanced than the white line' and I wonder why this is? Presumibly the white line was marked by the previous owner to indicate the standard timing position to use a strobe and if correct I cant see that it should ever be set more advanced than that. Normally you set the timing to this point and then retard it progressively to get any knocking to an acceptable level....

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4 minutes ago, johny said:

I see in the original post the timing is 'set 2 - 3 degrees more advanced than the white line' and I wonder why this is? Presumibly the white line was marked by the previous owner to indicate the standard timing position to use a strobe and if correct I cant see that it should ever be set more advanced than that. Normally you set the timing to this point and then retard it progressively to get any knocking to an acceptable level....

Thanks Johnny hadn’t give this a thought I do this change first as it’s the easiest ! 

I did advance because this was optimum tickover when moving distributor 

Many thanks 

Paul 

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Paul,

I note your original comment, and johny's, on setting the timing extra advanced.      I presume this is by the timing marks on the front pulley.

It is possible, I've seen it, for that outer ring, the damper, to slip round on the hub, so that the timing marks become a delusion.    If that happens, the damper become ineffective too.

To check, find true TDC and see if it coincides with the marks on the pulley.     Take out No.1 plug, position the crank about TDC, and put a long screwdriver in the plug hole, so that it sits on the piston top and sghows its movements.   Now adjust the position of the crank - a large spanner or socket on the hub bolt will turn it - to find true TDC.   It's fiddly, the piston moves more and more slowly as it approaches TDC and will stop over at least one degree at the critical point.      Now see if that agrees wth the pulley marking.

Good luck!

John

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I'm am no means an expert by any means on all the differentials on how, even our old cars are running, though with twin carbs, looking at the 3 seperate plugs can give an indication of separate, carb versus ignition issues. I THINK.

Dave    

Edited by daverclasper
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I notice you've got CDSEs, what condition are the rubber diaphragms in? Uncle Pete calls them elephant condoms. They should be soft and supple. There could also be a fuel line blockage issue, rubber slivers in the carb reservoir inlet or sludge in the fuel line.

Doug

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8 minutes ago, dougbgt6 said:

I notice you've got CDSEs, what condition are the rubber diaphragms in? Uncle Pete calls them elephant condoms. They should be soft and supple. There could also be a fuel line blockage issue, rubber slivers in the carb reservoir inlet or sludge in the fuel line.

Doug

Hi Doug the CDSE’s are in good order as in the past have suffered with slivers , sludge  from fake R9  tubing, sticking float valves etc though I will be checking the float valves again plus float height just in case . On the list is to compare the plugs as suggested in your recent post - Thanks 

Paul 

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